Yeah I see what you are saying and you are right. What you did is the adult mature thing to do.
Just based on her actions, it's pretty apparent that she hasn't reached that maturity level or she is really wrapped up in herself to be that indifferent about your feelings. She must have really been holding onto it for a long time to build up that kind of resentment. Another sign of emotional immaturity.
If you both haven't grown together as a couple, growing apart is probably the only option. If you feel like I felt, you might look back on it and think that she needed to grow for your relationship to work in the long run and that this split right now might be for the best. Maybe it's trying to put a positive spin on a very negative situation but that's how I felt. It takes two for a relationship to ultimately work, and if one is going the distance and the other isn't, it's going to fail.
And I say right now. Not to give you false hope, but anything can happen in the future.